Liquid metal forging process

ABSTRACT

Liquid metal forging process comprising pouring liquid metal into a mold, applying high pressure by a punch to said liquid metal through a sealing member of thin plate interposed between the pressure-applying surface of said punch and the liquid metal, wherein during pressing the rim of said sealing member because of high pressure and high temperature deforms and closely fits the mold to seal the clearance between the punch and mold against entrance of said liquid metal, thereby preventing the formation of flash.

United States Patent 72] Inventors Taikichi Awano;

Yoshihiro Oishi, both of Nagoya-shi, Japan [21] Appl. No. 793,757

[22] Filed Jan. 24, 1969 [45] Patented Oct. 19, 1971 [73] AssigneeKabushiki Kaisha Toyota Chuo Kenkyusho Hisakata, Showa-ku, Nagoya-shi,Aichiken, Japan [32] Priority Jan. 31, 1968 [54] LIQUID METAL FORGINGPROCESS 2 Claims, 6 Drawing Figs.

[52] US. Cl 164/120, 18/30 QZ, 164/312,164/319 [51] Int. CL B22d 27/12[50] FieldofSearch 164/113, 120, 312, 313, 319, 320; 18/30 02 [56]References Cited UN lTED STATES PATENTS 2,804,666 9/1957 Saives 164/3132,810,942 10/ 1957 Saives 164/313 2,932,865 4/1960 Bauer 164/1133,133,843 5/1964 Scherbner 164/120X FOREIGN PATENTS 50,004 3/1935Denmark 164/312 965,652 8/1964 Great Britain.. 164/312 908,322 9/1945France 164/312 379,702 8/1964 Switzerland 164/312 I Primary Examiner-R.Spencer Annear Attorney-Berman, Davidson & Berman ABSTRACT: Liquid metalforging process comprising pouring liquid metal into a mold, applyinghigh pressure by a punch to said liquid metal through a sealing memberof thin plate interposed between the pressure-applying surface of saidpunch and the liquid metal, wherein during pressing the rim of saidsealing member because of high pressure and high temperature deforms andclosely fits the mold to seal the clearance between the punch and moldagainst entrance of said liquid metal, thereby preventing the formationof flash.

LIQUID METAL FORGING PROCESS The present invention relates to animprovement in liquid metal forging in which molten or half-molten metalin a metal mold is pressed by a punch, or a plunger and solidified underhigh pressure to produce products in various desired shapes. Theapparatus used in the present invention utilizes a sealing member,interposed between said punch and said liquid metal which preventsleakage of the liquid metal into the clearance space between the moldand the punch, and thus, applies pressure from the punch to the liquidmetal more effectively and prolongs the life of the mold and punch.

Throughout the specification and the claims the term liquid metal" isdefined to include molten, half-molten, and partially molten metal to beforged.

In conventional metal forging, liquid metal is poured into a metal mold,and a punch of a size having a predetermined clearance with the wallsurface of the pressure portion of the mold is inserted therein. Highhydraulic pressure is then applied to the liquid metal by the punchuntil solidification of the liquid metal is completed. The resultantproduct evidences fine grain, compact internal structure. In order toretain the punch pressure (generally from 500 to 2,000 kg./cm.)effectively until the solidification of the liquid metal is completed,the clearance between the punch and the wall surface of the pressureportion of the metal mold is made as small as possible (from 0.01 to0.05 mm.), and the liquid metal, which is squeezed into the punchclearance space when pressure is applied, is quickly cooled and is madeto work as a packing, hereinafter termed "self-metal packing. However,there is a strong tendency for the packing to freeze the punch and moldtogether and when the punch clearance is too small, the wall surface ofthe mold and the punch come in contact with each other causing galling,and damage increases until the mold is broken by the tremendous frictionbetween the self-metal packing, or flash, and the mold. Anotherdisadvantage is that the pressure-effect of the punch is reduced, and itbecomes impossible to exert sufficient pressure to the central portionof the liquid metal because the surrounding portion of the liquid metalis quickly solidified, producing a resistance to pressure which the ramcannot overcome.

When the liquid metal to be forged is one of the metals belonging to thegroup of aluminum, or copper, the wear and damage to the mold isrelatively small, but when the liquid metal is one of the metals of theiron group, the hardness of the self-metal packing is remarkably high asit becomes iron oxide, or the like, and, therefore, the mold and thepunch are greatly damaged when pressure is applied, and often to anextent that they are usable only once and cannot be further employed. Ithas been suggested that a mold reinforcement be used in the form of anantiabrasive alloy such as a molybdenum alloy placed at the portion ofthe mold most subject to abrasion, but this has been found to be almostuseless. Especially, in forging liquid metals of the iron group, theabove mentioned disadvantages and drawbacks have led to poor results andno progress in the art of liquid metal forging.

In the present invention, the pressure is applied by the ram, orplunger, as in the conventional method, but a sealing member in the formof a metal plate is interposed between the liquid metal and the pressureapplying surface of the punch, and pressure is applied by the punch tothe liquid metal through sealing member. At that time, the sealingmember is plastically deformed by the resultant high temperature andhigh pressure, and the rim of the sealing member is thereby deformed toclosely fit to the wall surface of the pressure portion of the mold, andacts as a seal to prevent entrance of the liquid metal to the clearancespace between the mold and the punch. As a result, no flash is formed,abrasion and flash damage are prevented, and the pressure of the punchis more effectly applied to the liquid metal. The rim of the sealingmember has its hardness lowered by the high temperature, and movessmoothly in contact with the wall surface of the metal mold during theentire time the punch is being lowered.

From the above brief description it will be apparent that a primaryobject of the present invention is to provide an improvement in liquidmetal forging which will overcome the defects and disadvantages of thepreviously outlined conventional method of liquid metal forging.

Another important object of the present invention is to provide animprovement in liquid metal forging which permits the forging of metalsof the iron group without breakdown, or rupture, of the mold or thepunch except after repeated use, in contrast with conventional liquidmetal forging wherein the mold and associated parts can be used onlyonce.

The invention will best be understood from the following description ofspecific embodiments when read in connection with the accompanyingdrawings, wherein like reference characters indicate like partsthroughout the FIGS., in which:

FIG. 1 is a cross-sectional view of an apparatus used in an embodimentof the present invention;

FIGS. 2 and 3 are fragmentary sections similar to FIG. 1 showingapparatuses used in other embodiments; and

FIGS. 4 to 6 are sectional views of the FIG. 3 apparatus with the punchin successively lowered positions during the forging operation.

Referring now more particularly to the drawings, FIG. 1 illustrates theapparatus used in an embodiment of the invention differing fromconventional liquid metal forging apparatus in the addition of a thinmetal plate 12 to the punch 3. Plate 12 is temporarily adhered by meansof an adhesive, such as a resin, on the pressure applying end surface 4of the punch 3. The remainder of the apparatus which is conventionalincludes a metal mold 1 having a cylindrical molding space insidethereof, the upper portion of the cylinder being the pressure portion 2and the bottom portion thereof being the casting shaping portion orcavity 6. The molding space may have other and even irregularly shapedcross sections. The mold l is fixed on the base 8 by means of bolts 9.

In the conventional process, liquid metal 11 is poured into said moldand pressed with the punch, or plunger 3, capable of movinglongitudinally within the pressure portion 2 by fluid, hydraulic, or anyother pressure means, (not shown) until the metal is solidified into adense, fine grain, round bar. Nearly uniform clearance space 5 existsbetween the punch 3 and the wall surface of the pressure portion 2 andthe liquid metal passes into this space to form flash, as explainedabove. The knockout pin 10 is movable through an aperture in the base 8to lift the forged casting out of the mold 1 upon completion of theprocess of forging.

The thin metal plate 12 is made of a material whose melting point isalmost the same as, or higher than, that of the liquid metal 11 to beforged, and is shaped as a disk whose diameter is nearly the same as, orslightly larger than, that of the pressure portion 2. The rim 121 ofplate 12 is preferably inturned, or bent, in one direction. The thinmetal plate 12 is placed against and afiixed to the end surface 4 of thepunch in such a manner that the inwardly bent rim 121 faces toward thesurface of the liquid metal 1 l to be forged.

The disk 12 can be easily attached coaxially to the pressure applyingend surface 4 of the punch by fitting a central projection 31 of thepunch into a central hole 122 in the disk 12, as shown, for example, inFIG. 2. Alternatively, the disk 12 can be attached on the end surface 4of the punch by inserting therebetween a thin plate 13 of compressedglass fiber, or ceramic fiber, of virtually the same disklike form asthe metal disk, as shown in FIG. 3. The disk 12, with or without disk13, must be temporarily attached coaxially to the end surface of thepunch 4 by any suitable adherent means including the means mentionedabove, and or glue, adhesive, pins, bolts, or the like.

In use of the described inventive embodiments, when the punch 3 ispushed into the pressure portion 2 of the mold to press the liquidmetal, the gas at the surface of the liquid metal 11 escapes through theclearance space 5 past the bent rim 121 of the metal plate 12. When thepunch 3 is further lowered and the plate 12 touches the upper surface ofthe liquid metal 11, the temperature of the plate 12 is quickly raisedto the heat of the liquid metal and the plate 12 is plasticallydeformed. During lowering of the punch 3, the bent rim 121 of the plateis pushed upwardly and spread outwardly by pressure of the molten metal11 so that its outer edge fits closely against the cylindrical wallsurface of the pressure portion 2 of the mold. This prevents the liquidmetal 11 from leaking into the clearance space 5, as the entrance ofsaid clearance space is thus shut by the plate 12, and flash is notproduced. Consequently, damage to the metal mold usually caused by flashin conventional forging is avoided and at the same time the pressure ofthe punch 3 is effectively applied to the liquid metal because the edgeof rim 121 of the plate 12, contacting against the cylindrical wallsurface of the metal pressure portion of the mold is softened and movessmoothly therealong with a minimum of friction.

FlGS. 4 to 6 show successive positions of the punch in the mold and theresultant deformation of the thin plate 12 as the punch is lowered.Considering the forging of a metal in the iron family, preferably, plate12 is of stainless steel of 0.3 mm., thickness and is attached to theend surface of the punch 3 by a thin glass fiber plate 13 insertedtherebetween. The liquid metal 12 to be forged is molten cast iron andthe diameter of the cylindrical pressure portion 2 of the mold is 45 mm.

When the liquid metal 11 is compressed under pressure of 2,500 kg./cm.the stainless steel plate 12 contacts the liquid metal, and then theouter edge of rim 121 is pushed up and out by the pressure of the liquidmetal (as shown by arrows in FIG. 4) to closely fit the cylindricalpressure portion 2. Upon further downward movement of the punch, theplate 12 is further deformed under greater pressure as is shown in FIG.5, and finally takes the shape shown in FIG. 6.

The stainless steel plate 12 is softened by the high temperature, andits movement against the metal mold l is smoothly carried out, becausethe glass fiber disk 13 is melted and works as a lubricant to reduce thefriction between stainless plate 12 and the metal mold 1. After thepressing operation is completed, the stainless steel plate 12 is adheredto the upper surface of the product, but it can be easily removed bysimple mechanical processing, such as grinding, after the product isremoved from the mold.

It will be readily apparent from the above description that the presentinvention improves the conventional liquid metal forging process by useof a sealing member in the form of a thin metal plate attached to thepressure applying surface of the pressure punch for contacting thesurface of the liquid metal. The added plate prevents the fonnation offlash in the clearance space between the punch and the mold, and as aresult the friction between the flash and the metal mold is entirelyeliminated. Thus, the life of the metal mold is greatly prolonged. Atthe same time the pressure of the punch is retained without undue lossin overcoming flash-friction and is effectively applied to the liquidmetal. The operation is very easily carried out as described, and can beeffectively applied to all kinds of metals.

Although certain specific embodiments of the invention have been shownand described, it is obvious that many modifications thereof arepossible. The invention, therefore, is not intended to be restricted tothe exact showing of the drawings and description thereof, but isconsidered to include reasonable and obvious equivalents.

We claim:

1. A liquid metal forging process of the type including the steps ofpouring liquid metal into the cavity of a mold, applying high pressureto said liquid metal by a punch which is inserted into said cavity withclearance space, and compressing said liquid metal until it solidifies,the improvement comprising the step of inserting between the surface ofsaid liquid metal and a pressure applying surface of said punch a firstsealing member made of a metal plate having a surface area to fit thecross-sectional area of the mold and interposing between the firstsealing member and the pressure applying surface of said punch a secondsealing member made of a thin plate of a glassy substance having amelting temperature below that of the first-named sealing member andbelow the temperature of the metal to be forged, whereby said highpressure is applied through both said sealing members to said liquidmetal, while simultaneously sealing the clearance space between saidpunch and the walls of said mold against entrance of liquid metal bydeformation of the first sealing member to closely fit the mold, and themovement of said first sealing member along the wall of the mold islubricated by melting of said second sealing member.

2. The liquid metal forging process of claim 1, wherein is furtherincluded the step of adhering said first-named sealing member to thepressure applying surface of said punch with the second sealing memberinterposed therebetween prior to inserting the punch into the cavity ofsaid mold.

1. A liquid metal forging process of the type including the steps ofpouring liquid metal into the cavity of a mold, applying high pressureto said liquid metal by a punch which is inserted into said cavity withclearance space, and compressing said liquid metal until it solidifies,the improvement comprising the step of inserting between the surface ofsaid liquid metal and a pressure applying surface of said punch a firstsealing member made of a metal plate having a surface area to fit thecrosssectional area of the mold and interposing between the firstsealing member and the pressure applying surface of said punch a secondsealing member made of a thin plate of a glassy substance having amelting temperature below that of the first-named sealing member andbelow the temperature of the metal to be forged, whereby said highpressure is applied through both said sealing members to said liquidmetal, while simultaneously sealing the clearance space between saidpunch and the walls of said mold against entrance of liquid metal bydeformation of the first sealing member to closely fit the mold, and themovement of said first sealing member along the wall of the mold islubricated by melting of said second sealing member.
 2. The liquid metalforging process of claim 1, wherein is further included the step ofadhering said first-named sealing member to the pressure applyingsurface of said punch with the second sealing member interposedtherebetween prior to inserting the punch into the cavity of said mold.